Which structure in the lung is the primary site of gas exchange?

Study for the CAMLPR Histology Practice Test. Study with flashcards and multiple choice questions, each question has hints and explanations. Get ready for your exam!

Multiple Choice

Which structure in the lung is the primary site of gas exchange?

Gas exchange happens where oxygen moves from air into blood and carbon dioxide moves from blood into air, across a very thin barrier with a huge surface area. That occurs in the alveoli, tiny sacs at the ends of the airways, where the alveolar epithelium is directly juxtaposed with capillary endothelium. The respiratory membrane is extremely thin and the surface area is vast, so diffusion is efficient. Surfactant from type II cells helps keep these sacs open so diffusion can continue smoothly. The other structures serve different roles: bronchioles are mainly conducting airways (with limited gas exchange), the pleura are protective membranes around the lungs, and the trachea is the main airway conducting air to the lungs.

Gas exchange happens where oxygen moves from air into blood and carbon dioxide moves from blood into air, across a very thin barrier with a huge surface area. That occurs in the alveoli, tiny sacs at the ends of the airways, where the alveolar epithelium is directly juxtaposed with capillary endothelium. The respiratory membrane is extremely thin and the surface area is vast, so diffusion is efficient. Surfactant from type II cells helps keep these sacs open so diffusion can continue smoothly.

The other structures serve different roles: bronchioles are mainly conducting airways (with limited gas exchange), the pleura are protective membranes around the lungs, and the trachea is the main airway conducting air to the lungs.

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